Solar electrical systems and solar electrical systems with batteries, the latter of which are also referred to synonymously herein as solar-battery systems, have a number of components, illustratively including a solar array, a direct current-to-alternating current inverter (“inverter”), and a battery. Most batteries are added as retro-fits to existing solar systems composed of a solar array and an inverter. In many instances, additional components illustratively include a battery charger or a second inverter for power to and from the battery, respectively, are also included. To connect these different components electrically and safely, conduits and junction boxes are used. Most of these components are in different enclosures connected by conduits and are typically wall-mounted.
However, recently more integrated systems have appeared on the market where some or all of the components are housed in a closed electrical cabinet to avoid the need for conduits and to reduce the footprint of the system. The closed cabinets are either electrical cabinets of the traditional rack type, as shown in prior art FIG. 1A, or are adapted or custom cabinets that use some type of shelf or magazine-style structure, as shown in prior art FIG. 1B.
The closed electrical cabinets are then filled with the required components to create a solar-battery system based on the given application and include an inverter of a certain power rating, at least one battery, and other required components. In the rack-type system of FIG. 1A, components are mounted onto the vertical rails of the rack with screws or pins. The rack-type system is the most common type of electrical cabinet where rails are typically spaced 19 inches (48 cm) apart. The mounted components can be full-width 21, or half-width 22, or of any other fractional size. The situation is similar with shelf or magazine-style cabinets, as shown in FIG. 1B where components fill a full shelf 24, or half-a shelf 26, or any other fraction of the cabinet width.
The electrical components of such prior art racks or cabinets are then connected to one another through a wire harness that provides power, and in some instances communications links between the components. The prior art rack or cabinet is then connected to the solar array, the grid, the electrical load, combination thereof, or possibly other components to form a complete solar-battery systems.
Most electrical components generate so much heat that they must be cooled through convection of air through the cabinet, by heat sinking the components to the outside of the cabinet, or to an air duct passing through the cabinet, but where the air duct is exterior to the cabinet itself. The components of the cabinet can also be cooled by a system that contains a cooling liquid. Cabinets with an air duct that is external to the interior of the cabinet keep the cabinet interior clean of dust and free of moisture and are thus particularly useful. The disadvantage of air duct-style systems is that all components when inserted into the cabinet need to be thermally connected to the air duct. Achieving a reliable and consistent thermal contact when installing components at an end-use site can be difficult.
Most of the aforementioned cabinets are shipped empty in order to save weight, but may include all or part of the cable harness and other components such as the fan, which do not contribute much weight. However, a cabinet holding batteries can exceed safe lifting limits. The specific weight of a lithium-ion battery (with enclosure, battery management system, and other protective and analytic electronics) is in the range of 10-15 kilos per kilowatt-hour. Solar-battery systems designed for residential or small commercial use are typically of the order of 10 kWh, and the system battery weight alone is in the range of 100-150 kg. A solution to the problem of battery weight is thus to “load” the components, especially the batteries, into the cabinet at the site of use.
However, the installation of the components at the site of use makes the use of air duct cooling more difficult, because all components need to make good thermal contact to the air duct. To achieve good thermal contacts, components need to make firm physical contact with the air duct and/or a thermally conductive paste may be applied between the component and the air duct wall. Firm contact is achieved through screws, clamps, and the like.
A fundamental shortcoming of the rack of shelf/magazine-style cabinets is the fact that when shipped to the site the cabinet is a voluminous element with relatively little value per volume. This results in high shipping costs. Large cabinets are also unwieldy to transport and often shippers apply extra cost to voluminous items, which further increases the cost per shipped value. In general, voluminous freight is difficult to handle and is often damaged during transport, which results in returns or delays, and, as a result, customer dissatisfaction.
Yet another shortcoming of a traditional cabinet is that the cabinet must be either sized to hold exactly the number of components needed for the application, or will otherwise contain some empty space. The empty space could be used for expansion of the system, for example for the addition of more batteries, but the finite size of the system also means that the amount of expansion is limited by the size of the cabinet. As a result, offerings from vendors for solar-battery systems include a collection of cabinets to accommodate various system sizes. In addition, at the site of use cabinets that are not fully filled, take up unnecessary space.
The two primary reasons vendors choose a cabinet over components in separate enclosures are that the inside of cabinet conduits can be replaced with a wire harness which is cheaper and simpler to assemble or change, and the second reason is that inside a cabinet a central cooling system can be used—otherwise each component must have its own fan or other passive cooling system.
Thus, there exists and need for an electrical system for a solar installation that overcomes at least one of the aforementioned short-comings of the prior art. There further exists a need for an electrical system that provides improved air cooling of the components in such an electrical system without resort to customization.